The invention relates to bins for holding lumber. The application has specific application to bins for holding sorted lumber.
Lumber bins with so-called xe2x80x9clive bin wallsxe2x80x9d are used for holding lumber in various places in sawmills. A series of such bins may be used, for example, to hold various grades of sorted lumber. Canadian patent No. 1,264,772 discloses a bin sorter having bins separated by bin walls. Each bin has a floor which can be lowered to a lumber discharge station. A gate extends from the bottom of each wall. The gates function to control the discharge of lumber from individual bins onto a conveyor.
When lumber is discharged from a bin of the type described in Canadian patent No. 1,264,772, the lumber sometimes spills onto the conveyor in a way that can damage the lumber.
There is a general need for lumber bins which can effectively hold quantities of lumber and then discharge the lumber, when desired. There is a particular need for such bins which reduce damage to the lumber during discharge of the lumber.
The invention relates to bins for holding lumber and methods for operating lumber bins. One aspect of the invention provides a lumber handling apparatus. The apparatus may be a bin sorter apparatus. The apparatus comprises upstream and downstream bin walls having lower edges and a conveyor extending below lower edges of the upstream and downstream bin walls. The conveyor is movable in a downstream direction. A lumber support is located between the bin walls. The lumber support movable upwardly and downwardly between a first position wherein the lumber support is between the bin walls and a discharge position wherein a lumber supporting surface of the lumber support is below the lower edge of the downstream bin wall. A first gate is movable between an upright position wherein the first gate projects above the level of the conveyor to substantially block lumber from passing between the lower end of the downstream bin wall and the conveyor and a lowered position wherein the first gate is below the level of the conveyor. Lumber can be discharged by lowering the lumber support to the discharge position and then lowering the gate so that the lumber is carried over the lowered gate by the conveyor.
The first gate may be pivotally mounted to a support for rotation about a pivot axis below the level of the conveyor.
Another aspect of the invention provides a method for operating a lumber handling apparatus. The apparatus comprises a bin having upstream and downstream bin walls. The method comprises placing a quantity of lumber on a downwardly movable lumber support surface in the bin between the bin walls and moving a gate to an upright position. In its upright position the gate substantially blocks a gap between a conveyor and a lower edge of the downstream bin wall. The method lowers the lumber support to a discharge position and moves the gate downwardly to a lowered position below a level of the conveyor. The method then carries the lumber on the conveyor downstream from the lumber support and over the gate.
Further aspects of the invention and features of specific embodiments of the invention are described below.